Hooking up with someone for one night of sex with no strings attached and hoping to never see them again. It is important not to exchange any personal info with them so they can't track you down and stalk you later.

Sexual activity with another person intended for one night only. (Derives from showbiz, a "one-off show". But also of course from the suggestion of a one-off erection, though the term is used by women as well as men as a candid description of "getting your rocks off" when a bit of no-strings fucking etc. was desired.

“I've never had a one-night stand because I've always been afraid that in the cold light of day, she'll wake up and think; "Oh my God! What the hell am I doing in bed with a stupid cunt like this?!”